Duration of the second-stage labor
Eight trials involving 1809 women were included in this outcome, 1723 women contributed data. The result of meta-analysis indicated that women in lubricant group had a shorter duration of the second-stage labor when compared with those in standard care group (MD -13.72 minutes, 95%CI -22.68, -4.77; I2=98%; very low certainty due to serious risk of bias, serious inconsistency and serious imprecision) (Table 1, Figure S26).
Subgroup analyses showed that there was significant subgroup effect between lubricant type subgroups (Pinteraction=0.02) (Figure S27), and not between overall risk of bias subgroups (P interaction=0.37) (Figure S28). Subgroup analysis according to lubricant type indicated that obstetric gel (MD -16.9 minutes, 95%CI -27.03 to -6.78) had a shorter duration of the second-stage labor than liquid wax (MD -8.38 minutes, 95%CI -11.11 to -5.65). The heterogeneity of high risk of bias groups was reduced after subgroup analysis (I2=65%), while significant heterogeneity remained within low high risk of bias groups (I2=99%). This heterogeneity might partially result from studies of low high risk of bias (Figure S28).
The result analyzed based on parity indicated that nulliparous women in lubricant group had a shorter duration of the second-stage labor when compared with those in standard care group (MD -14.46 minutes, 95%CI -24.58, -4.34; I2=98%) (Figure S29). There was insufficient data to perform subgroup analysis for this outcome for multiparous women.